1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to level shifting and rectifying circuits.
2. Description of the Related Art
Increasing processing speeds of devices such as graphics processors, hard disks, network cards, and other high-speed I/O devices have created a need for an increased bandwidth for communicating between devices. One way to increase bandwidth between the bridge circuit and the I/O device is to use a differential communication link such as PCI (Peripheral Component Interface) Express, HyperTransport, SATA (Serial Advanced Technology Attach), USB (Universal Serial Bus), and other suitable differential communication links. Such interfaces may utilize a flexible, hybrid serial-parallel interface format that uses multiple differential communication links often referred to as lanes. Each link may include transmit lanes to transmit information and receive lanes to receive information.
During certain modes of operation such as during a non-transmission mode, a low power mode, and/or other suitable modes of operation, the transmit lanes may be clamped (e.g., coupled) to the same voltage (e.g., common mode voltage). As such, a receiver associated with the receive lanes may detect this mode of operation by sensing a differential voltage swing of the differential communication link. For example, the receiver may be able to detect that the transmit lines are clamped when the voltage swing is less than a low threshold and that the transmit lines are not clamped when the differential voltage swing is greater than a high threshold. Other techniques may be used to determine a mode of operation as well.